1. Field of the Invention
The present invention is broadly concerned with improved labeling devices designed for use with packaging equipment. More particularly, the invention is concerned with transverse labeling devices of the kind typically used with in-line packaging machines such as form, fill and seal machines and wherein the labeling devices are simpler and can be more readily cleaned and serviced, as compared with existing labelers. The preferred labeling devices of the invention also are readily adjustable so as to accommodate packages of varying sizes, leading to reduced cycling times while essentially eliminating variations in labeling impacts.
2. Description of the Prior Art
U.S. Pat. No. 6,543,505 describes highly successful Crossweb™ labeling devices designed to apply labels on-line to packages in form, fill and seal thermoform packaging machines. The devices of the '505 patent are capable of using labels of a single roll and to apply the labels at a 90 degree angle to any package array. The device uses separate stepper motors for label web advancement and label peeling, for transporting, separating and applying the labels, and for selectively indexing the entire system to label multiple rows.
As described in the '505 patent, the label tamping assembly makes use of an enclosed box with fans attached to create a vacuum which holds separated labels to transport belts. A plurality label tamp blades are positioned within the box and are connected to an air cylinder actuator. In operation, separated labels are positioned on the transport belts and the blades are shifted so as to move the labels into contact with the packages. Use of the enclosed vacuum box presents several problems. Any labels that are not properly adhered to the packages tend to be drawn back into the fan box by the fans, eventually blocking the fans and requiring the entire system to be cleaned out to remove the waste labels. Additionally, these labelers are often used in food plants (e.g., for the labeling of meat or cheese packages), necessitating daily equipment washdowns. The enclosed space defined by the vacuum box in these labelers thus presents a sanitation issue.
Additionally, in the current labeling devices the transport and tam ping assembly is rigidly mounted to the frame of the labeler which is then mounted across either the top or the bottom of a packaging machine (depending upon which side of the packages are being labeled). Owing to variations in the frames of the packaging machines and the depths of different product packages, the tamp unit stroke must be long enough to reach a variety of distances. Usually, the stroke length will have a length of at least 200 mm, and sometimes up to 250 mm. The required tamp stroke is typically restricted only by the package labeling surface and the air cylinder itself does not normally extend its full stroke. In order to regulate the impact strengths of the tamp unit between different packages, flow control restrictions and precise regulation of the cylinder valve firing time are used.
These expedients present a number of practical problems. The first is tamp cycle time. The longer the stroke of the label tamp, the slower the machines cycle time will be. Another problem is variation in impact strength of the tamp, i.e., attempts to control the impact strength using time and flow controls makes the system very dependent on constant air pressure from a plant source, which is often not reliable. Thus the first tamp of a cycle tends to be stronger than the subsequent tamps, due to pressure buildup in the system.
An additional problem with conventional labeling equipment stems from the use of conventional, imperforate rollers in the label-handling apparatus. Such rollers tend to become fouled with scrap labels making them difficult to clean and maintain. A related issue is that such rollers are supported on regular bearings which are themselves hard to adequately clean. Thus, there is a tendency towards accumulation of bacteria on these bearing assemblies. Prior art rollers are not designed for such easy cleaning and sanitation, see, e.g., U.S. Pat. Nos. 3,991,440, 5,306,131, 6,149,755, 6,126,583, 5,358,233, 6,432,030, 5,388,489, 5,414,914, 5,736,089, 5,649,890, 5,021,111, 4,868,958, 4,584,747, 4,607,947, 3,597,818 and 4,848,079.
There is accordingly a need in the are for an improved labeling device which overcomes the problems inherent in the use of a vacuum-box type of tamping unit, while moreover alleviating problems associated with rigid mounting of the transport and tamping assembly, such as cycle times and variable impact strengths. Additionally, there is a need for improved roller devices for use in the label transport assemblies of labelers which can be more readily cleaned and maintained.